Here we explore the implications of our TRM for ecosystems and for the future of insect biodiversity.
Task 4.1: A resilience risk map for insect-mediated ecosystem functions. Species are often the focus within conservation biology, but system-level properties determine the delivery and resilience of ecosystems and natural capital. Combining our best estimates of recent (T3.3) and historical (T3.4) changes in insect biodiversity with data on functional traits (T1.4), we will quantify changes in the structure of multivariate trait space over time, to infer resilience of ecosystem function.
Task 4.2: Network properties and ecosystem stability. The structure and complexity of biotic interactions among species of different functional guilds plays a fundamental role in community organisation and ecosystem stability. Here we seek to tease apart the significance of biological interactions as both a predictor of insect declines and a determinant of resilience.
- What are the leverage points of network (re)configuration? Ecosystem resilience and robustness in response to species loss/gain, as well as changing interaction strength, will be formulated using the modelling framework of Adaptive Dynamics, with options of interaction rewiring and species (categorized in trait space) addition or removal. We will test for cascading effects using knowledge from the TRM about covariance in threat-response relationships of functional groups, combined with well-resolved quantitative ecological networks (T1.5). Specifically, we will explore, using simulations, the effects of selective species removal on the topology and stability of ecological networks (e.g. connectance, modularity and nestedness) and biomass flux between guilds. We will extend this concept to explore cascades between networks - cross-ecosystem subsidies - that result from species existing in multiple ecosystems across their life-cycle (e.g. Odonata), and how life-history switch points respond to changes in network components.
- What are the drivers of network dissimilarity? Zeta diversity can be expanded to explore interaction dissimilarity between networks of different locations or times. Coupled with generalised dissimilarity modelling, we will explore which processes (e.g. disturbance) are responsible for network dissimilarity and changes of interactions. When combined with question T4.2a, we will reveal the anthropogenic pressures that reshuffle particular network components, violating the stability criterion and leading to (partial) collapse/reorganisation.
Task 4.3: The future of insect biodiversity and ecosystem function. We will use the outputs of WP3 to project insect biodiversity under future scenarios of environmental change. The posterior distributions of the Bayesian belief network will be projected to establish the best, most comprehensive estimate of insect trends for any given location and period of time. Building on our previous work on the role of climatic extremes on observed insect trends, we will project the specific taxon-driver response models from WP2 to predict biodiversity under future scenarios for particular pressures individually or in combination, propagating uncertainty throughout. Future projections for important pressures, including for land use and climate, are available both globally (tinyurl.com/tanpq67; tinyurl.com/v3wckcg) and in greater detail for UK (tinyurl.com/rmszlwa), and will be combined with proxies for other environmental drivers (T3.4; T1.3). By projecting the TRM onto multiple future scenarios of change, the resulting projection maps will identify past and future hotspots of insect decline. We will use both exploratory scenarios, and also normative scenarios that explore insect biodiversity under a set of alternative futures. In addition, we will project the interaction dissimilarity model (T4.2b) onto these future scenarios to identify network components that are under stress and could lead to potential regime shift in ecosystem functioning. We anticipate that future environmental change will lead to a substantial reshuffling of interactions, with potential knock-on consequences for other components of diversity.